Conventionally, a sheet using a thermoplastic resin is used for various applications. The thermoplastic resin itself is water repellent and thus a problem in terms of water resistance hardly arises. The water absorption rate of the sheet, however, is significantly increased by blending inorganic particles and carrying out stretching treatment.
Therefore, in the case of aiming at improving brightness and opacity by blending the thermoplastic resin with the inorganic particles and carrying out the stretching treatment, an increase in water absorption rate is required to be reduced.
For example, Patent Literature 1 discloses a thin film material for processing containing a thermoplastic resin and an inorganic substance powder in a weight ratio of 18:82 to 50:50. According to Patent Document 1, the thin film material can reduce a degree of water absorption by stretching the thin film material about 1.2 times to about 4.0 times so that the specific gravity becomes 1.4 or smaller and 0.6 or larger.